1. Field of the Invention
The present invention relates to a method of driving an ink jet recording head and a recording apparatus which employs the driving method and, more particularly, to an ink jet recording head which can reduce a period of time necessary for a discharge stabilizing process, such as recovery of ink discharge and preliminary discharge of ink, and can reliably execute that process, a method of driving the ink jet recording head, as well as a recording apparatus which employs the recording method.
2. Related Background Art
One ink jet recording technique involves supplying ink from an ink tank into liquid passages of an ink jet recording head, and subjecting the ink in the liquid passages to mechanical energy produced by electro-mechanical transducers such as piezoelectric elements, or thermal energy produced by electro-thermal transducers such as a pyrogenic elements (see U.S. Pat. No. 3,747,120, U.S. Pat. No. 4,723,129, etc.). Ink is thus discharged from discharge openings in communication with the liquid passages so that an image in the form of characters or graphics is formed on a recording member (e.g., recording paper).
The inner diameter of the liquid passages and the diameter of the discharge openings are often very small, in the order of about 50 .mu.m, for example. Therefore, if the period in which no ink is discharged (i.e., recording stop period) is prolonged, the position of an ink meniscus may be moved back from the discharge opening into the liquid passage, or the viscosity of ink remaining in the ink jet recording head may be increased due to drying attendant on evaporation of ink. In such a condition, no ink will be discharged from the discharge opening or unstable discharge will occur even when sufficient mechanical or thermal energy is applied to the ink. The occurrence of such non-discharge or unstable discharge condition makes it difficult to obtain good image recording.
In order to solve the above problem, it has been proposed to count the time of the recording stop period and eject ink from a nozzle (discharge opening) when the counted period exceeds a predetermined time, or preliminarily eject ink from the nozzle upon a printing command being applied after the recording stop period has lasted beyond a predetermined time, as disclosed in U.S. Pat. No. 3,925,788 and U.S. Pat. No. 3,925,789 by way of example.
Alternatively, U.S. Pat. No. 4,712,172 discloses a technique to apply electrical energy to an electro-thermal transducer to an extent that ink will not be discharged, and then carry out preliminary ink discharge.
While such preliminary discharge operation can always permit good recording of an image such as characters or graphics, an attempt at prolonging a period of the preliminary discharge operation or shortening intervals between the preliminary discharge operations is made to assure more stable image recording for a longer term.
However, there may occur some disadvantages if the preliminary discharge operation is carried out for a sufficiently long period or with short intervals.
For example, the preliminary discharge period is usually set to about 1-1.2 sec. However, periods of time in this order often give users a waiting time that they may find awkward, particularly for equipment such as electronic calculators and typewriters which are required to make records on recording paper quickly in response to keys being depressed on a keyboard, or those devices which are designed to perform high-speed continuous recording.
Further, the preliminary discharge for a sufficiently long period or with short intervals results in a large amount of ink being accumulated in an ink collector for collecting ink of preliminary discharge. In case of the collector formed of an absorber, there may occur a risk of ink which has been absorbed in the absorber overflowing and staining the interior of the unit or flowing out to the exterior.
Another problem is that the use of large amounts of ink for the preliminary discharge wastes a large amount of ink, which prevents the efficient utilization of ink, particularly in a system of the on-demand type.